This invention relates to the art of supplied air breathing apparatus and, more particularly, to a valve cartridge assembly for the pressure regulator in such apparatus.
It is of course well known to provide supplied air breathing apparatus of the character including a source of breathing gas supplied to the user of the apparatus through a pressure regulator or pressure demand valve which is connected either directly or through a hose to a face mask worn by the user and which is responsive to the user's inhaling and exhaling so as to provide the appropriate flow rate of breathing gas to the user. Pressure demand valves for use with such breathing apparatus often include a diaphragm actuated flow control valve which opens and closes in response to inhaling and exhaling by the user such that breathing gas from the source flows to the face mask or face piece worn by the user during inhaling and stops during exhaling. Examples of such pressure regulators or pressure demand valves in supplied air breathing systems are shown in U.S. Pat. No. No. 2,951,494 to Holmes; U.S. Pat. No. 3,097,638 to Streimer; U.S. Pat. No. 3,783,891 to Christianson; U.S. Pat. No. 4,041,978 to Leemann; U.S. Pat. No. 4,094,314 to LeCornec; and, U.S. Pat. No. 4,971,050 to Bartos.
In use of supplied air breathing apparatus including a pressure regulator of the character shown in the foregoing patents, the diaphragm actuated flow control valve within the regulator is subjected to relatively rapid wear as a result of the number of cycles of operation of the control valve during use thereof. For example, if the user is breathing at a medium rate of 20 to 30 breaths per minute, for example, the flow control valve cycles 100 to 150 times during five minutes of use of the breathing apparatus. Furthermore, the component parts of the flow control valve are subjected to moisture and other contamination during use of the breathing apparatus. As a result of such wear and contamination, the component parts of the flow control valve most often deteriorate to a point requiring repair or replacement long before other parts of the pressure regulator require repair or replacement. Moreover, in many pressure regulators, the flow control valve is not readily accessible for inspection or cleaning, whereby deterioration is accelerated.
Heretofore, deterioration of component parts of the flow control valve has required either replacement of the pressure regulator in its entirety, or rebuilding of the flow control valve portion of the pressure regulator if accessible. In this respect, if the component parts of the flow control valve are not accessible for repair or replacement work, then the entire pressure regulator must be replaced. Even if the component parts of the flow control valve are accessible, repair or replacement thereof involves a time consuming, piece-by-piece disassembly and reassembly of the component parts of the valve and, upon reassembly, calibration of the valve to assure proper operation thereof in conjunction with subsequent use of the pressure regulator. Furthermore, such disassembly and reassembly of the component parts may be so time consuming as to render replacement of the entire pressure regulator more economical than repair of the flow control valve portion thereof. In either event, the cost is undesirably high. Moreover, repair and replacement of component parts of the flow control valve cannot be achieved in the field, or by the user who lacks technical knowledge or experience required in connection therewith, whereby such maintenance requires return of the pressure regulator to a suitable shop for such work which results in a loss of the availability of the breathing apparatus to the user for the period required to rebuild and return the pressure regulator.